One Chance
by Art-Over-Matter
Summary: The world has six days left before everything is destroyed, and Mark is left as one of the only ones able to fix it before it's too late... This is the game One Chance if it happened IRL (and if Mark Fischbach was never a YouTuber). If you're not familiar with Once Chance, you might have a harder time understanding this, but you can give it a go.
1. Prologue

It was almost one o'clock in the morning and Mark Fischbach was the last one in the lab.

There was a way. There _had _to be a way.

He tried to believe it with every ounce of his soul, but his faith in science was failing. His faith in…luck…was failing. He felt so desperate and alone, there was nothing to hold onto anymore. There existed something to hope for, but nothing to base that hope upon.

Everything—literally _everything_—depended on him now. He only had a few hours left, and he was now questioning his decision to leave his wife and daughter at home.

There had to be a way.


	2. Day One

**Six Days Earlier...**

When Mark went upstairs to say goodbye to his wife before heading to the lab for the day's work, the first thing he heard was Molly, his daughter, crying.

"It's okay, sweetie," he heard Penny's voice attempting to soothe her, "anything that's ever done can be undone. It'll just take some time."

Mark peeked his head around the door to Molly's room. "What happened?"

His wife looked up to him, shaking her head. "Molly tried to cut her own hair."

Mark couldn't help but smile slightly. He looked down at his daughter and her red-brown hair that she'd gotten mostly from her mother. Surely enough, there was a lock of it that was at least half the length of the rest, hanging down awkwardly in the seven-year-old's face.

Molly looked up at him with dark chocolate brown eyes that nearly mirrored his own in color. She looked quite upset.

Mark crouched down to see eye-to-eye with her and gave her a warm smile. "Hey, it's not a bad thing. None of the other girls in your class have cool hair like this, huh?" He picked up the strand and barely managed to tuck it behind her ear. "You'll be fine, sweetie. Just don't use the scissors without your Mom's permission, okay?"

Molly nodded, sniffling, and bounced forward to hug Mark. He wrapped his arms around her and smiled, raising his eyebrows to look up at his wife.

When Molly had backed away, Mark stood up and kissed his wife on the cheek. "I'll see you this evening, honey."

"Have a good day at the lab. I know you'll figure out that cure."

Mark smiled. "Thanks."

"Bye, Daddy," Molly said, going back to stand next to her mother.

What Mark found when he entered the lab was nothing he ever could have predicted. It was utter chaos. There was an unusual number of cars leaving the parking lot when he pulled up, and when he went into the building, he found people rushing around right and left, most of them wearing surgical masks or using some other type of cloth to cover their mouths.

Mark stood, semi-frozen, staring at the panic for a few seconds before a woman he didn't recognize came up to him.

"You were working on the project to cure cancer, weren't you, Fischbach?"

Still barely coming to his senses, Mark nodded.

"Your department fucked up," she said, all professionalism disregarded. "The disease can kill everything. Every living cell they've put next to it." Without saying any more, the woman brushed past Mark and left the building.

_Disease? _The cure wasn't a disease….Unless things had gone even worse they could have imagined.

As Mark started to head toward the lab where he usually spent most of his days at work, he noticed his boss approaching him from a separate hallway. He was one of the few people not wearing anything to cover his face.

"Mark. Everything's gone wrong. We've set loose a virus and it's destroying everything it can find. Every living cell. It hasn't killed anyone yet, but it has the potential to, very quickly." He pinched the bridge of his nose, more resigned than panicked, though he too seemed afraid, like everyone else. "We don't think there's any way to stop it from spreading."

"How did it get out of the lab?" Mark asked, his eyebrows knitted.

"We don't know. Probably on one of the scientists, or just through the air. It doesn't matter now. If I were you, I would get out of here."

"But what if there's a way to stop it?" Mark said, his voice starting to take on an unexpected hysterical note.

"It's spread too fast! We probably only have a few days before everything in the area's destroyed, including you and me."

"How much can it spread? Does it reproduce quickly?"

"I don't know, Mark. Some of the researchers on our team are staying behind to see what they can do about it. A lot of them are leaving. What you do is your choice."

Mark nodded vaguely. His mind was already made up.

He headed straight for the lab.

Mark almost didn't want to go home that evening. He couldn't help but feel that if he went to see his wife and daughter again, he would condemn them to certain death. But he knew the virus wasn't like that. His action of carrying it home would make no difference; it was probably already there, and the concentration of it was irrelevant.

The news had been flooded with stories of E48K15. Mark knew Penny would already know about it, but strangely enough, she hadn't called him.

When he stepped into his house around dinner time, his wife met him right at the door. Molly, who usually greeted her father quite ecstatically at the door, was nowhere to be found.

"What are we going to do?" Penny asked in a quiet tone. There was no greeting.

Mark shook his head and looked at the ground. "There's nothing we know of yet. I—I don't know what we're going to do." He looked up. "Did Molly overhear the news?"

She shook her head. "Maybe parts of it, but she definitely has no idea what it means. When is the lab going to figure things out, Mark?"

His already remorseful expression fell even more. "We made absolutely no progress today. I don't know when we're going to find anything out." If _we're going to find anything out._

She continued to pepper him with questions for some time, until Molly opened the mudroom door and peeked her head in.

"Mommy, can I come yet? Hi Daddy!"

Mark gave his wife a glance that said 'we'll talk about it later' and went to fully open the door. "Hi, Molly. Sorry, Mommy and I were just talking about boring parent stuff."


	3. Day Two

Mark went to the lab early the next morning; before his wife had even woken Molly up so she could get ready for school. His vocal exchanges with his wife were either falsely 'normal' or darkly solemn.

As Mark drove to the lab, he remembered something he'd heard his wife say the day before. _"Anything that's ever done can be undone."_

If that was true, then by god, Mark was going to find a way to stop the virus.

Mark and the part of the laboratory team that had come to continue the research found little information that day—certainly no hint at something that would kill E48K15.

"Is anything looking better?" Penny asked through the phone as he drove home.

As Mark's eyes scanned the twilight-lit road in front of his headlights, he couldn't help but notice that there seemed to be fewer cars around than there usually were at this time of day. "No." He paused for several moments before speaking again. When he did, his voice was weak. "We estimated it would take five more days for the virus to take over the entire country. At that point, it would be irreversible and—the entire world would suffer the effects."

He wasn't sure if the noise he heard was a gasp or a mild cry of horror. "Oh, god, Mark, no!"

"Yes," he whispered to himself, knowing that the sound wouldn't carry through the call. Then, louder, "Honey, I c—can't talk to you right now. I'm sorry. I'll tell you more when I get home." He ended the call and dropped his phone onto the passenger's seat.

He could barely see the road through his tears.


	4. Day Three

Sleep was a hard thing to find when the entire world was inches from hell. It had taken Mark until 11:50 the previous night to fall asleep, and when he awoke, the red numbers glaring through the dark read 2:38.

He awoke with a start and a nauseous feeling in his gut. He turned onto his side and tried to just close his eyes and relax, but the image of what he'd just seen—and the fact that it was a very real possibility—forbade him from returning to sleep.

Mark sat up and rubbed his face in his hands. How could this have happened? Their brilliant cure for cancer—the potential world phenomenon that could have been able even to cure the common cold, was not only a failure, but an unfathomable danger. To everything. To Mark's wife and, probably even more importantly, his daughter.

He could still see the image from his nightmare—Penny and Molly dead on the floor of the house, all their living cells destroyed and all because of him….

"Mark?" a groggy voice said beside him.

"Yeah," he answered.

"Why are you awake? Are you okay, honey?" She clicked on the dim bedside lamp.

No, Mark realized. He was not okay. Nothing was okay.

He shook his head, suddenly unable to speak. His hands were involuntarily running through his hair. This was all his fault. This was literally, undeniably, his fault. He and the researchers in his lab were the cause of what could be the end of the world.

Mark didn't even know how to comprehend that.

"What is it?" Penny asked, sitting up so she could see his face.

"I can't—I don't know how to—" He shook his head again. "People are dying because of me. Everything is dying because of me."

"You didn't know…." His wife seemed not to know how to say more. It wasn't as though she could argue with him.

Mark looked at her, though his lack of glasses prevented him from seeing her face clearly. "We have no way to fix this." His voice was starting to become choked, the tightness in his throat making every word a small struggle. "I don't think we could possibly come up with a cure in time."

Penny looked at the bed sheets. "You still have four days, maybe longer."

"But how long will it take for the disease to reach here? How long until it reaches Molly?" Mark's voice broke and his resolve followed suit. His fingers were tangled in his hair as his body began to leak despair from his eyes.

Penny embraced him, but it hardly made him feel better. All his mind could do was ask how long her loving touch would last.

Fewer people showed up to the lab that day, when Mark went in after getting no sleep since he woke up from his nightmare. His best friend Wade was there to work again, but Bob—Mark's other best friend—had learned that E48K15 had found its way to his family, and had chosen to skip work, probably forever. Mark wished he could do the same.

They worked tirelessly, inching closer but coming up empty-handed. The only useful information to be found that day was from a different group of scientists in California, who had studied victims of E48K15 and discovered that those who got decent amounts of sleep seemed to be putting off the symptoms of the disease better than others. Even then, such information would only be known to the general public the next day.

After another hundred thousand had already died.

When Mark got home that night, more distraught than ever, he and Penny decided it would be prudent for her and Molly to go get checked for the virus the next day. Mark was terrified to know what the results would be, but it would be best, perhaps, to have a warning if either of them was about to die.

Mark could test himself in the lab, and while it probably wasn't the safest idea—while he had helped create the disease, he'd never actually dealt with it in the human body—he refused to go anywhere but the lab for the rest of the week. After all, the rest of the week was all he had, unless he died earlier than that.


	5. Day Four

"Daddy, do I have to go to school today?" Molly asked, her snippet of hair hanging in her face again. It was earlier than the youngster usually got up, but Mark had awoken early again, drowning in the bed sheets and in terror, and he and Penny had been loud enough when they went downstairs that they had woken her up.

Mark glanced to his wife. "Does she, Mommy?"

Penny sighed, trying to keep her expression neutral. "No, Molly. The school…called yesterday. You don't have to go. Besides, we do have somewhere to be today."

"Is it somewhere fun?" Molly asked with a hopeful, childish grin.

Penny's face fell. "I—uh, not exactly, sweetheart. But maybe afterward we can go out to get something nice to eat."

"Will Daddy get to come?" she asked, looking back to Mark.

Mark shook his head, keeping his expression level with a small smile. "No, honey. Sorry. I'm gonna work late tonight again. The lab's very busy still."

The girl's face saddened into something between disappointment and poutiness. She said quietly, "I still don't know what's wrong at your lab."

Mark's throat tightened. He knew Molly wasn't dumb; she could sense something was wrong between her parents, and she'd figured out it centered on the lab.

"It's nothing you'll need to worry about," Mark tried to assure her.

Tried.

But failed.

_x_

Mark tested his blood for traces of the disease while waiting for a part of an experiment to finish. The results came up positive. Not that it was surprising; how could he not have it after working day in and day out with the microscopic horrors?

He didn't bring the subject up with Wade. Everything had already been difficult between the two of them lately, just because they were so weighed down by everything. Their friendship wasn't failing. But they were having a hard enough time staying motivated to keep trying—every time they started to talk about anything other than work, they both began to feel depressed, which was the last thing they needed.

_"__Anything that's done can be undone." _Mark still thought of that sometimes.

Before he'd left work that afternoon, he got a call from Penny. She was crying when he answered.

"Honey?"

"Mark? She's got it. Oh god, Mark, Molly's got it…." It took her until after a few sobs to speak again. "They said she probably only has a day or two. What am I supposed to do?"

Mark felt tears dampen his eyelashes. He put his head down in the hand not holding his phone, wrapping his thumb and forefinger around his forehead. "Just try to stay calm, Penny. Does Molly have any idea?"

"She's in the car with me right now, but I made her put headphones in—I don't know if she can hear what I'm saying." She was having a hard time forming words. "She knows something's wrong, but I don't know how much."

"Okay, well, she'll have to know at some point. Baby, try to breathe….What were your results?"

"I've got it too, but I have longer than she does."

Mark's tears were running down his face, but he tried to keep his shit together. "Penny, I'm sorry. You have to know, I am so, so sorry. I can't even express how much I—"

"You didn't know, Mark…" she said, though it was a very half-hearted attempt at comfort.

"I'm going to figure it out. I'll be here for as long as I have to. I'm going to find something, Penny. There's got to be a way."


	6. Day Five

Penny wasn't feeling well when Mark was getting ready to leave the next morning. He couldn't help but notice that her complexion was paler and more gray-tinted than usual.

"Mark."

He wasn't even wearing work clothes; all he was doing was eating breakfast. No one cared what he wore; his boss hadn't been at the lab for the last three days anyway.

"Yes?"

Penny walked into the kitchen. "Don't go today. There's no point. Everything is pointless. Besides, you know that if someone else happens to find a cure, you have to rest. You can hold off the effects of the disease. You know you have it."

Mark had to admit to himself that it was tempting. His lab wasn't coming up with a cure; he could just leave it to people on the other side of the country, who probably didn't have E48K15 yet.

But no. Not only did his lab know more about it than any other, but he knew that he couldn't live with himself if he didn't put every single ounce of effort he had into finding a cure. If there was a cure.

"No, honey. I'm sorry, but I have to go. I can't just give up."

"But it's so pointless, Mark! We only have two days left. Can't you at least stay home with me and Molly?"

The pain in Mark's chest was trying to convince him to stay. But logic told him there was still a chance, and he had to do everything to use it.

He turned fully to his wife and hugged her. "I have to find the cure, Penny. I'm going to work until I find it."

_Or until I can't anymore._


	7. Day Six

It was almost one o'clock in the morning and Mark was the last one in the lab.

_There's a way, _he told himself. _There has to be a way._

He tried to believe it with every ounce of his soul, but his faith in science was failing. His faith in…luck…was failing. He felt so desperate and alone, there was nothing to hold onto anymore. There existed something to hope for—the cure—but nothing to base that hope upon.

Everything—literally everything—depended on him now. He only had a few hours left until statistics ruled that a cure was useless, and he was now questioning his decision to leave Penny and Molly. Couldn't he have chosen to spend his last moments with them?

Mark was feeling the effects of the disease now. He felt constantly slightly nauseous and he had the worst headache he'd ever experienced. If he moved too fast, he'd start to feel dizzy. He had no idea how he could get anything done while in this state, but nonetheless, he was giving it everything he had left.

He had seen the E48K15 get destroyed by a different microorganism, but the E48K15 had killed it too fast for it to be effective. If only the microorganisms could reproduce faster….

Forty minutes later, after three more hastily done experiments, Mark ran the numbers through the computer again. The graph opened up on the screen.

Mark stared at it.

It worked. The numbers checked out. This cure could actually combat E48K15 faster than E48K15 could kill cells.

He'd found it.

_x_

As much as Mark wanted to call and talk to his wife, he had to get the cure distributed through the air first. Just letting it out of the lab would be enough to get it started—it spread even faster than E48K15. Opening up the lab took time, but Mark worked as quickly as his weary body could handle.

As soon as the cure was in the air, Mark got into his car with a liquid form of the cure in a box next to him. He immediately picked up his phone and called Penny.

No answer.

There was no one on the road around him, no tree still alive in the park he passed on his way back to his house. He called his wife twice more, but again, no answer.

Mark refused to consider what this might mean. He wouldn't think of it. He couldn't.

The house was dark and silent as he drove up to it. As he parked in the driveway and got out, a sense of inexorable dread settled around him like silent snow.

The euphoria he'd felt at finding the cure had been quenched immediately upon not getting a call from his wife. His mood was sinking even lower now, as he entered the house through the garage door.

"Penny? Molly?"

He heard something rustle in the living room and he followed the sound to the couches.

"Mark? It's so late…."

He pulled Penny into a hug as soon as she stood up off the loveseat. "Why the hell didn't you answer my calls? Where's Molly? Is she okay? I found the cure, Penny!"

"You—you what?"

"I found it," he said, though his energy was suddenly starting to fade. The euphoria had returned, but his enthusiasm was dampened ever so slightly by sudden weariness.

Penny didn't seem to know how to react. Mark knew she didn't disbelieve him, but he knew she'd given up all hope prior to this. "M—Molly's in her room, she's fine as far as I know, though neither of us have felt great." She spoke absentmindedly. "I had just collapsed onto the couch after I put Molly in bed….Is the cure out? Can you use it?"

He nodded. "But I have it here too just in case," he said, pulling out a syringe of the dilute solution that included the microscopic saviors. "It only attacks the E48K15. And as far as I know, it should be flushed out of your system within a few days."

After Mark carefully injected his wife with the cure, the two of them made straight for Molly's room.

"Molly?" Mark said softly, not turning on the ceiling light since he knew it would be a rude awakening.

The girl stirred. "Daddy?"

Mark smiled and flicked on the pink bedside lamp. "Sit up and give me your arm, sweetheart. This won't hurt."

Molly blearily rubbed her eyes and sat up. "What is it, Dad?"

"Just something you need. I'll make you feel better." Mark's vision spun slightly as he gently took his daughter's arm and injected her with the cure. His headache was pounding now and he could hardly hear his own thoughts. "There you go. You can go back to sleep now." He kissed the top of her head and left the room, turning the lamp out before he went.

"Mark, you look terrible," Penny realized upon seeing Mark leave Molly's room.

He nodded. "I've been awake for twenty hours now. I'm not surprised," he admitted wearily.

She frowned, following him as he went back to the living room and settled onto one of the loveseats. "But the cure will still work on you. You've already injected yourself, right?"

He shook his head. "I didn't bother." He looked up at her, uncertain how to feel. "I haven't had any good rest in the past three days, Penny. And that was the only thing ever found to combat the disease." He took off his glasses and set them on the arm of the couch, pinching the bridge of his nose as he closed his eyes. "No, I never gave myself the cure. It was too late. I can just hope that it's not too late for the majority of everyone else."

Tears sparkled in Penny's eyes. She didn't ask what he meant—she knew.

She spoke in a near whisper. "I have a way we can find that out."

Before Mark responded, she left the room and came back a few seconds later, carrying a laptop. "Someone will get our Internet back on. It's the best way to communicate to people, so it should be a priority."

He nodded, glad that he'd have some way to know if all his work had paid off not just for his family, but for the world population.

It was a strange feeling when Mark started to notice his body shutting down.

First it was that he had a hard time moving his arms and legs. Shortly after, he noticed that the nausea he'd been feeling for the past six hours had disappeared.

"Mark, it's back. The Internet's on and people have already realized a cure is out."

Mark let out a breath he hadn't thought his lungs had the capacity to hold in—it was becoming increasingly difficult to breathe. The contented relief he felt in that moment was incomparable to anything he'd ever felt before.

He smiled slightly and repositioned so that he was lying on his back on the loveseat, his legs draped over the arm. It felt odd to move when he could hardly feel the lower half of his body.

"You did it!" Penny started happily, before shutting the computer and seeing Mark's obvious discomfort. "Oh, god, no. Honey?"

"It's fine. It's all fine," Mark assured her, though he couldn't keep himself from being at least a little bit afraid.

Penny knelt on the floor next to Mark's head and started to run her hand through his unruly hair. It didn't take long before she was crying. "I'm sorry this is what it t-took. I'm s-sorry for everything."

"No regrets, Penny, please. I wish I could be here for Molly, but if this was the only way, I wouldn't have anything else, really."

Mark closed his eyes and for a moment, he thought that would be the last thing he ever said. But one last thing occurred to him and he had to speak again.

"Penny?"

Her voice was shaky with sobs. "Yes?"

"When you tell Bob and Wade about what's happened to me, just…try to break the news…gently. You know how much those two mean to me."

Mark cracked an eye open to see Penny nod.

"Thank you."

Not long after those words, Mark's awareness faded.

And with it, his life.


End file.
